A number of people gather around a table and work together in various situations. Various studies have been conducted that consider a table as a tool for the people to work together and aid such cooperative work using the tool by a computer. Examples of such studies include studies about CSCW (Computer Supported Cooperative Work) and group wares.
Digitizing work on the table is advantageous for example in that the work process can be recorded electronically or information can be shared among remote places. Images displayed according to conventional studies are usually projected on a table by a projector or the table itself is made of a display such as an LCD (Liquid Crystal Display). In any of these cases, two-dimensional images are displayed.
Using such two-dimensional images, only document type information can be presented and stereoscopic type, three-dimensional shape information cannot be presented. In addition, when a single two-dimensional image is displayed, some of the people gathering around the table see the information upside down depending on the seating arrangement, which makes it hard to see the information.
In order to solve the former problem, a method of having a person wear a special pair of glasses to make a two dimensional image appear three dimensional has been suggested. According to the method, however, it is necessary to display a two-dimensional image while tracking the positions of people, which limits the number of participants or there is still some awkwardness caused by wearing the glasses, and it should hardly be natural observation of three-dimensional images.
In order to solve the latter problem, a system has been suggested in which a square table has its top surface made of a special screen to provide viewers positioned in the four different directions around the table with different images. In this case, a two-dimensional image is presented in each of the four directions, and therefore a special pair of glasses is necessary to make an image appear three dimensional.
A multi-direction real image display has been suggested that allows images to be viewed from multiple directions by arranging a plurality of CRT (Cathode Ray Tube) video displays, a plurality of mirrors for turning light paths back and a plurality of convex lenses in an annular shape (see Patent Document 1). However, the multi-direction real image display simply presents a plurality of two-dimensional images using the plurality of CRT video displays.
In the meantime, a system has been suggested that provides an image in the air based on an image displayed on a display using a relay optical system including lenses or mixes the image into a background using a half mirror. Using such a system, an image appears as if it is floating in the air, and therefore a pseudo-stereoscopic feeling can be obtained. However, what is presented is still a two-dimensional image and could not appear stereoscopic enough. Positions where a person can observe such an image are limited to particular viewing locations. Therefore, a plurality of people cannot view the image with ease.
A method of reconstructing a pseudo spatial image by projecting an image on a screen composed of a rotating disk or a plate movable in the front-back direction has been suggested. According to the method, a number of people can share and view a pseudo three-dimensional image by the naked eye. However, in order to present a three-dimensional image on a table, the screen as described above must be provided on the table. This limits a space available for work on the table.
[Patent Document 1] JP 2003-15081 A